摘要:

Reactive oxygen species including superoxide and hydrogen peroxide are important mediators in atherogenesis. We investigated the enzymatic source of vascular superoxide and its role in endothelium-dependent vasorelaxation during neointima formation. Silastic collars positioned around carotid arteries of rabbits for 14 days induced neointimal thickening. Using lucigenin-enhanced chemiluminescence, superoxide production was detectable in collared artery sections, but not in controls, only after inactivation of endogenous Cu2+/Zn2+-superoxide dismutase (Cu2+/Zn2+-SOD) with diethyldithiocarbamate (DETCA). Dihydroethidium staining indicated that endothelium and adventitia were the major sites of superoxide generation. Superoxide production in DETCA-treated collared arteries was enhanced further by NADPH and was inhibited by diphenyleneiodonium, suggesting NADPH oxidase was the source of the radical in collared arteries. Moreover, real-time PCR demonstrated 11-fold higher expression of the gp91phox subunit of NADPH oxidase in collared arteries than in controls. In vascular reactivity studies, endothelium-dependent vasorelaxation to acetylcholine did not differ between collared and control sections. However, treatment with DETCA reduced relaxations to acetylcholine in collared rings, but not in controls. NADPH further reduced relaxations to acetylcholine in DETCA-treated collared sections, but not in controls. In DETCA/NADPH-treated collared rings, sensitivity to nitroprusside, in contrast to acetylcholine, exceeded that of controls. Moreover, further treatment of such rings with exogenous Cu2+/Zn2+-SOD restored acetylcholine relaxations without altering nitroprusside responses. Thus, early neointimal lesions induced by periarterial collars are associated with elevated gp91phox expression and increased NAPDH-oxidase-dependent superoxide production in endothelium and adventitia. However, endothelium-dependent vasorelaxation is largely preserved due to the actions of Cu2+/Zn2+-SOD and increased smooth muscle sensitivity to nitric oxide.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

It has been suggested in isolated porcine cerebral arteries that stimulation by nicotine of &agr;7-nicotinic acetylcholine receptors (&agr;7-nAChRs) on sympathetic nerves, but not direct stimulation of parasympathetic nitrergic nerves, caused nitrergic neurogenic dilation. Direct evidence supporting this hypothesis has not been presented. The present study, which used in vitro tissue bath and confocal microscopy techniques, was designed to determine whether choline, a selective agonist for &agr;7-nAChRs, induced sympathetic-dependent nitrergic dilation of porcine basilar arterial rings. Choline and several nAChR agonists induced exclusive relaxation of basilar arterial rings without endothelium. The relaxation was blocked by tetrodotoxin, nitro-l-arginine, guanethidine, and &bgr;2-adrenoceptor antagonists. Furthermore, the relaxation was blocked by methyllycaconitine and &agr;-bungarotoxin (preferential &agr;7-nAChR antagonists) and mecamylamine but was not affected by dihydro-&bgr;-erythroidine (a preferential &agr;4-nAChR antagonist). Confocal microscopic study demonstrated that choline and nicotine induced significant calcium influx in cultured porcine superior cervical ganglionic cells but failed to affect calcium influx in cultured sphenopalatine ganglionic cells, providing direct evidence that choline and nicotine did not act directly on the parasympathetic nitrergic neurons. The increased calcium influx in superior cervical ganglionic cells was attenuated by &agr;-bungarotoxin and methyllycaconitine but not by dihydro-&bgr;-erythroidine. These results support our hypothesis that activation of &agr;7-nAChRs on cerebral perivascular sympathetic nerves causes calcium influx and the release of norepinephrine, which then act on presynaptic &bgr;2-adrenoceptors located on the neighboring nitrergic nerve terminals, resulting in NO release and vasodilation. Endogenous choline may play an important role in regulating cerebral sympathetic activity and vascular tone.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We investigated the possibility that the TRPC gene family of putative store-operated Ca2+entry channels contributes to the increase in microvascular endothelial permeability by prolonging the rise in intracellular Ca2+signaling. Studies were made in wild-type (wt) and TRPC4 knockout (TRPC4−/−) mice and lung vascular endothelial cells (LECs) isolated from these animals. RT-PCR showed expression of TRPC1, TRPC3, TRPC4, and TRPC6 mRNA in wt LECs, but TRPC4 mRNA expression was not detected in TRPC4−/−LECs. We studied the response to thrombin because it is known to increase endothelial permeability by the activation of G protein-coupled proteinase-activated receptor-1 (PAR-1). In wt LECs, thrombin or PAR-1 agonist peptide (TFLLRNPNDK-NH2) resulted in a prolonged Ca2+transient secondary to influx of Ca2+. Ca2+influx activated by thrombin was blocked by La3+(1 &mgr;mol/L). In TRPC4−/−LECs, thrombin or TFLLRNPNDK-NH2produced a similar initial increase of intracellular Ca2+secondary to Ca2+store depletion, but Ca2+influx induced by these agonists was drastically reduced. The defect in Ca2+influx in TRPC4−/−endothelial cells was associated with lack of thrombin-induced actin-stress fiber formation and a reduced endothelial cell retraction response. In isolated-perfused mouse lungs, the PAR-1 agonist peptide increased microvessel filtration coefficient (Kf,c), a measure of vascular permeability, by a factor of 2.8 in wt and 1.4 in TRPC4−/−; La3+(1 &mgr;mol/L) addition to wt lung perfusate reduced the agonist effect to that observed in TRPC4−/−. These results show that TRPC4-dependent Ca2+entry in mouse LECs is a key determinant of increased microvascular permeability.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Osteopontin (OPN) is a soluble secreted phosphoprotein that binds with high affinity to several integrins and it has been found at the site of atherosclerotic lesions. However, the role of OPN expression in vivo is still poorly understood. To investigate the physiological role of OPN in detail, we generated transgenic mice (Tg) overexpressing the OPN gene under control of the cytomegalovirus enhancer/chicken &bgr;-actin promoter. We detected OPN mRNAs in almost all tissues of 3 lines of Tg mice by Northern blotting. The serum levels of OPN were significantly higher in Tg than in non-Tg mice (782±107 versus 182±44 ng/mL;P<0.001). Compared with non-Tg mice, a 73% (88±6 versus 51±7 &mgr;m;P<0.001) and 94% (126±15 versus 73±11 &mgr;m;P<0.0001) increase in the medial thickness of the aorta was determined in Tg mice at 16 and 32 weeks after birth. However, we found no evidence of inflammatory cells adhering to endothelial cells, intimal hyperplasia, or calcification in any region of Tg mice without artery injury. We then investigated the effect of cuff-induced injury to the femoral artery. The intimal thickening in Tg mice increased 2.9-fold more than that in non-Tg mice (4.9±1.9 versus 1.7±0.4 &mgr;m;P=0.022). The expression of OPN induces both medial thickening without injury and neointimal formation after injury, thus suggesting that OPN plays a role in the development of atherosclerosis, vascular remodeling, and restenosis after angioplasty in vivo.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID